1. Field of the Invention
The present invention relates to a method of segmenting a lesion in an image and, more particularly, to a method which can automatically detect a boundary of a lesion in an ultrasound image of a breast.
2. Description of the Related Art
Due to changes in dietary life and decrease in breast feeding, the incidence of female breast cancer has increased over previous years. Especially, the breast cancer has recently become a very important part of many female cancers as the incidence rate of breast cancer has ranked the first among all of the female cancers and the mortality rate has ranked the second in the world.
When a primary tumor having a size of 5 mm to 2 cm is found, the cure rate increases, and thus the early diagnosis of breast cancer is very important. Once a small tumor is found in the breast, it is determined whether the tumor is benign or malignant by periodically observing the shape of the growing tumor, and then it is determined whether to perform surgery.
Diagnostic imaging technologies, in which electronic engineering, computer engineering, physics, medicine, physiology, etc. are combined, have been led by the developed countries with advanced industrial technologies, extensive experience in management of high technologies, and a market from which enormous research and development costs can be recovered.
At present, the diagnosis of breast cancer is made mainly by breast X-ray imaging or two-dimensional breast ultrasound. The X-ray imaging has advantages such as high resolution, low noise, and easy detection of calcification which often occurs in a tumor. However, the lesion and the breast tissue where the lesion is located are all shown as white, and thus it is difficult to accurately identify the position of the lesion and, in the case of women with dense breast tissue, this identification is more difficult.
In addition to the above-described problems, there is a serious problem such as radiation exposure. Even with a small amount of radioactivity, the radioactivity may be another cause of breast cancer and the risk is greater in the case of lactating women. For these reasons, the early diagnosis of breast cancer using the X-ray imaging is not easy to perform.
In the case of ultrasonic images, the calcification is hardly found, but the breast tissue is shown as white and the lesion is shown as dark. Thus, it is easier to find the lesion. Most of all, the screening for breast cancer can be easily achieved even in the case of dense breast tissue. Moreover, the fact that the ultrasonic is harmless to humans increases the possibility of early diagnosis and allows patients to undergo medical examinations for suspicious spots more frequently, thereby increasing the accuracy of the diagnosis.
For an accurate diagnosis of cancer, it is necessary to observe the change in shape and size of a lesion at a predetermined interval of time and, to this end, it is necessary to constantly detect the boundary of the lesion. However, when a doctor draws the boundary directly by hand, it is difficult to quantitatively express the change in shape, size, etc.
In order to automatically segment the lesion, there is a method of segmenting a lesion using a threshold value based on the idea that the inside of a lesion is dark and the outside thereof is light. Since an ultrasonic image has much noise due to its nature, filtering is used to remove noise from the image, and then the threshold value is applied to the image. However, in the case where the inside of the lesion is not uniformly dark, it is difficult to determine an appropriate threshold value even after the filtering, and thus a satisfactory result may not be achieved.
Moreover, a method of multiplying an image by a Gaussian shape is used to prevent the case where the shape of a lesion is not defined within a region of interest due to several factors such as noise. However, according to this method, the Gaussian shape has a great influence on the shape of the lesion, and thus the lesion may lose its original shape.